The surge in the violence coincided with military drills launched by the Armenian military.

Armenia on September 2 accused Azerbaijan of deliberately escalating tensions on the border in an "attempt to thwart Karabakh peace talks."

Ethnic Armenian separatists backed by Yerevan seized control of the territory during a 1990s war. Despite years of negotiations, the two countries have not signed a final peace deal to cement a tenuous 1994 ceasefire.